Regression in individuals with Rett syndrome.

Data on features of regression and pre-regression developmental history in a case series of 53 girls and women with Rett syndrome are presented. Consistent with the diagnostic criteria, hand skills and verbal or non-verbal communication skills were the most common skills lost during regression. Play and motor skills were also lost in half the cases. Regression most commonly occurred between 12 and 18 months of age but was noted in a few cases before 6 months or after 36 months. Pre-regression developmental delays or abnormalities were noted in over two-thirds of cases, increasing to 85% of the youngest cases where parental reporting was likely to be more accurate. Age at regression was not associated with severity of physical and growth symptoms, and thus did not appear to be an index of neurological severity. There is a continuing need to further elucidate the pre- and post-regression features of Rett syndrome in order to aid early identification, diagnosis and referral for genotype mutation analysis.